if you already have wired the controller n1 and the controller n1 is also the same type of controller, the procedure is exactly the same.
just 1 thing differ, the bidirectional data wire.
check wich wire from the controller n1 is soldered to the bidirectional data wire pin at the gamecume mobo side.
then you will know wich color is, then wire the second controller to the exactly same pins you wired the controller n1, but solder the bidirectional data wire to the player 2 bidirectional data wire pin at the gamecube mobo.
this is easier to see with images
player 1 setup
[common part for all controllers]
as you can see, the ground pins at the gamecube mobo are pins 2 and 8, you also can wire it to any other ground point of the gamecube mobo.
the 3.43v logic suply is located at the pin n6 of the gamecube mobo
the 5v suply is located at the pin n1 of the gamecube mobo
if your controller have cable shielding you can also solder it to the ground pins
[specific controller part/wire (AKA bidirectional data wire)]
the bidirectional data wire of the controller player n1 must be wired to the pin n 10 of the gamecube mobo
the bidirectional data wire of the controller player n2 must be wired to the pin n 7 of the gamecube mobo
the bidirectional data wire of the controller player n3 must be wired to the pin n 4 of the gamecube mobo
the bidirectional data wire of the controller player n4 must be wired to the pin n 3 of the gamecube mobo
note: I also noticed the controllers 1 and 2 have an extra pin at the mobo (pins 6 and 9) of the mobo, anyway I never used them while making my portable and it seemed to work perfect, not sure if they have any ussage for other devices than normal controllers, such gba + the cable to connect it to the gamecube wich is used on games like zelda windwaker and zelda four swords.
